• T Eastlund, A Van Duren, and M E Clay.
• Transfusion Medicine Section, Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis, MI 55455, USA. eastlund@usa.redcross.org
• Vox Sang. 1999 Jan 1; 76 (4): 216-9.

Background And ObjectivesWhile blood is flowing within a transfusion-warming device, the blood temperature is usually less than that applied externally. If the flow is temporarily stopped, the temperature can rise above 37 degrees C in some warming devices. We sought to determine whether temperatures near 45 degrees C achieved during prolonged non-flow conditions in a blood warmer are harmful to red cell integrity.Materials And MethodsAfter 42 days of storage at 4 degrees C, red cells were exposed to 44.7 degrees C for 30 min while stationary in a blood warming device (Augustine Medical, Inc., 241 Fluid Warming Set) and examined for cell counts, hemolysis and osmotic fragility.ResultsRed cell, white cell and platelet counts, hemoglobin, PCV and potassium were unchanged following heat treatment. Plasma hemoglobin was 508+/-132 mg/dl following heat treatment compared to 396+/-188 for the control (p>0. 05). In the osmotic fragility test, hemolysis remained within normal limits when tested at 0.60 and 0.65% sodium chloride (NaCl) and was unchanged at the 0.5% NaCl level. At the 0.75% NaCl level, there was 16+/-5.1% hemolysis of heated 42-day-old red cells compared to 11+/-3.4% for the control (both of which being above the 9% upper limit for fresh control red cells).ConclusionsWe conclude that elevated temperatures achieved during temporary cessation of flow in the Augustine Medical, Inc., 241 Fluid Warming Set for as long as 30 min do not cause notable hemolysis or other damage to red cells.

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